This invention relates to an integrated circuit and may be advantageously applied to, for example, a rotary head digital audio tape recorder adapted for generating various sensor detection signals.
Conventionally, in a rotary head digital audio tape recorder (R-DAT), audio data is adapted to be recorded and/or reproduced on or from a magnetic tape wound on a rotary head. In the R-DAT, the recording/reproducing timing of the rotary head, the relative speed between the rotary head and the magnetic tape, and rotary head tracking or the tape running speed, are controlled with the aid of sensor output signals obtained from a variety of sensors provided in a drum driving the rotary head into rotational movement, and from a capstan and supply and take-up reels for the magnetic tape.
More specifically, the drum for driving the rotary head into a rotational movement includes a drum phase sensor formed by small magnetic pieces secured to the outer peripheral part of the drum, a magnetic head for detecting the passage of the small magnet pieces, and a drum frequency sensor in the frequency generator configuration. The drum phase signal and the drum frequency signal, obtained as output signals from the associated sensors, are transmitted to the downstream side drum phase detection signal generating circuit and drum frequency detection signal generating circuit, respectively.
The capstan and the magnetic tape supply and take-up reels are provided with a capstan frequency sensor, a supply reel frequency sensor, and a take-up frequency sensor, each in a frequency generator configuration respectively. The capstan frequency signal, supply reel frequency signal, and the take-up reel frequency signal, obtained as the output signals from these sensors, are transmitted to a capstan frequency detection signal generating circuit, a supply reel frequency detection signal generating circuit, and a take-up reel frequency detection signal generating circuit on the downstream side, respectively.
Meanwhile, the drum phase detection signal generating circuit, drum frequency detection signal generating circuit, capstan frequency detection signal generating circuit, supply reel frequency detection signal generating circuit, and the take-up reel frequency detection signal generating circuit are designed and constructed so that the input sensor output signals are amplified and converted into binary signals with a predetermined threshold level as the boundary; and the produced drum phase detection and drum frequency detection signals, capstan frequency detection signal, supply reel frequency detection signal, and the take-up reel frequency detection signal are transmitted to a drum servo circuit, capstan servo circuit, and supply and take-up reel motor control circuits, respectively.
In the above described R-DAT, it may be contemplated that if the five sensor detection signal generating circuits, that is the drum phase detection signal generating circuit, drum frequency detection signal generating circuit, capstan frequency detection signal generating circuit, supply reel frequency detection signal generating circuit, and the take-up reel frequency detection signal generating circuit could be formed on one integrated circuit, the circuit configuration may be simplified so that the R-DAT as a whole may be further reduced in size.
However, in practice with the drum phase detection signal signal generating circuit and the drum frequency detection signal generating circuit, the input frequencies are low and on the order of tens to hundreds of kilohertz, whereas the input signals are of small amplitudes on the order of tens to several microvolts and hundreds to several microvolts, respectively. Thus, an amplifier of an extremely high gain is necessitated for outputting the detection signals in the form of 0 to 5 V digital signals.
On the other hand, the capstan frequency detection signal generating circuit generates a signal of a large amplitude with an input level of several to tens of millivolts, whereas the supply reel frequency detection signal generating circuit and the take-up reel frequency detection signal generating circuit generate signals of large amplitudes with an input current of not lower than 30 microamperes, so that they are each formed by an amplifier with a broader operating margin.
Hence, if these five sensor detection signal generating circuits are simply mounted on an integrated circuit, the large amplitude input signals to the supply reel frequency detection signal generating circuit or to the take-up reel frequency detection signal generating circuit may be occasionally input into the drum phase detection signal generating circuit or into the drum frequency detection signal generating circuit to give rise to inconveniences such as oscillations or the like which interfere with the smooth and stable operation of the integrated circuit in its entirety.